Oyster knife



FIG. 1 is a front, right side, top perspective view of an oyster knife showing my new design;

FIG. 2 is a front elevational view thereof;

FIG. 3 is a rear elevational view thereof;

FIG. 4 is a left side elevational view thereof;

FIG. 5 is a right side elevational view thereof;

FIG. 6 is a top plan view thereof; and,

FIG. 7 is a bottom plan view thereof.

The broken lines depict portions of the oyster knife that form no part of the claimed design. 

CLAIM The ornamental design for an oyster knife, as shown and described. 